In the field of electrical lighting, many different types of lights sources have been developed over the years. Recently, fluorescent light fixtures have been developed to take advantage of the greater electrical efficiency provided by such lights. Fluorescent lamps are negative differential resistance devices, so as more current flows through them, the electrical resistance of the fluorescent lamp drops, allowing even more current to flow. Connected directly to a constant-voltage power supply, a fluorescent lamp would rapidly self-destruct due to the uncontrolled current flow.
To prevent self-destruction, conventional fluorescent lamps must use a ballast to regulate the current flow through the lamp's glass tubes. However, when the ballasts and other components break down and require replacement, repair of the fluorescent light can be costly in terms of both parts and labor. Also, disposal of fluorescent lamps raises environmental issues because of their mercury content.
To address the problems associated with fluorescent lamps, LED lamps are now widely accepted as a more efficient and environmental friendly light source than fluorescent lamps. LED lamps allow electrical current to pass through the device in one direction while blocking current flow in the opposite direction. LED lamps provide many advantages as a lighting alternative compared to fluorescent lamps. Some benefits of using LED lamps include no mercury, operation in extreme cold conditions, longer life, and better energy efficiency.
To gain acceptance in the marketplace in terms of consumer safety, lighting fixtures are required to comply with regulatory standards established by organizations such as Underwriters Laboratories Inc. (UL) and International Electrotechnical Commission (IEC). One such set of standards is UL 1598C that governs electrically-active parts during installation of the LED lamps into existing fluorescent fixtures. To prevent the risk of fire and shock, these regulatory standards specify that there shall not be electrical continuity between the two ends of the tube during the insertion. Namely, the two ends of the tube must not be electrically connected during the insertion. The electrical current should not energize the LED light tube before it is completely installed in bi-pin sockets of the fixture.
During installation of a conventional replacement LED lamp, an exposed electrical pin presents a risk of shock to a user. Typically, when replacing, for example, an LED lamp including bi-pin end caps, the user inserts the first pair of pins at one end of the LED lamp into one electrical socket in the fixture, and then inserts the second pair of pins at the other end of the LED lamp into the other electrical socket in the fixture. When the first pair of pins is inserted into the socket, the second pair of pins is exposed because they are not yet inserted into the other socket. Although the LED lamp is shut off and deactivated, the internal electronic circuitry is still live and energizes the exposed pins. As a result, the user will be shocked if the exposed pins are touched.
To satisfy the required UL 1598C standards and to leverage the benefits of the fluorescent lights, most lighting manufacturers produce retrofit kits to install LED components in existing light fixtures. However, many of these kits require modification to the existing fixtures, and some still potentially create the risk of fire and shock. Often, highly trained technicians are required to perform these modifications. Thus, retrofitting and rewiring existing fluorescent fixtures can be quite expensive. Some manufacturers produce retrofit kits with two safety switches positioned at each end of the LED tube to attempt to protect against the risk of shock. Unfortunately, some of these LED tubes with double-ended safety switches still pose safety hazards. During a lamp replacement, insertion of one end of the tube into the lamp holder automatically arms the tube by pressing the switch, which creates the risk of shock if the pins at the other ends are touched.
In addition to addressing the risk of shock, efforts have been made by lighting manufacturers to provide a LED lamp that is simple enough for ordinary consumers to replace. Another problem associated with replacing fluorescent lamps is that each type of fluorescent lamp is designed with different electronic ballasts to properly start and operate the lamp. Today there are hundreds of different types of fluorescent lamps including different types of ballasts available on the market, which requires ballast manufacturers to carry an expansive inventory of ballast types. The most common electronic ballasts are switch start (preheat), rapid start, program start, and instant start.
A switch start (preheat) electromagnetic ballast uses a combination filament-cathode at each end of the lamp in conjunction with a starter switch that initially connects the filaments in series with the ballast, thereby preheating the filaments prior to striking an arc tube. The starter switch closes, permitting a heating current to flow through each electrode. The starter switch triggers the supply voltage to be applied across the arc tube to initiate the discharge. The electrode heating power is turned off after the lamp discharge is initiated.
A rapid start electronic ballast uses filament power windings within the ballast to provide a low voltage to the lamp prior to lamp ignition. The ballast applies voltage and heats the cathode simultaneously. The rapid start electronic ballast continues to heat the lamp electrodes even after the lamp is started.
Program start electronic ballasts include circuitry to preheat the lamp filaments to apply cathode heat before lamp ignition, and then remove it once the lamp is ignited. The ballast applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc.
Instant start electronic ballasts do use filaments to provide ignition. The ballasts of these tubes do not preheat the electrodes. Rather, they use a high voltage to break down the gas and mercury column to initiate the discharge arc. These tubes can be identified by a single pin at each end of the tube or a shunted lamp holder.
The above-described shortcomings significantly limit the replacement of fluorescent lamps with LED lamps within existing lamp fixtures. Therefore, there remains a need for a consumer friendly apparatus and method for conveniently replacing fluorescent lamps with LED lamps into existing lamp fixtures without modifications, yet complying with regulatory requirements. There also remains a need for a system and method of providing a replacement LED lamp compatible with various types of fluorescent ballast systems.